TN 

948 
M7K6 


Kithil 


Monazite,  Thorium  and 
Meaotboriua 


THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 

LOS  ANGELES 


The 


DKI'AKIMI 

UNIVERSITY 

U)S  ANGELES.  CALIF  . 


1  U.  C.  L  A.  DUPLICATE 

Technical  Paper  110  Mineral  Technology  8 

DEPARTMENT    OF   THE    INTERIOR 
BU  RE  AU     OF     MINES 

JOSEPH   A.  HOLMES,  DIRBCTOR 


MONAZITE,   THORIUM,   AND 
MESOTHORIUM 


BY 


KARL  L.  KITHIL 


WASHINGTON 

GOVERNMENT  PRINTING  OFFICE 
1915 


The  Bureau  of  Mines,  in  carrying  out  one  of  the  provisions  of  its  organic  act— to  dis- 
seminate information  concerning  investigations  made — prints  a  limited  free  edition 
of  each  of  its  publications. 

When  this  edition  is  exhausted  copies  may  be  obtained  at  cost  price  only  through 
the  superintendent  of  documents,  Government  Printing  Office,  Washington,  D.  C. 

The  superintendent  of  documents  is  not  an  official  of  the  Bureau  of  Mines.  His  is 
an  entirely  separate  office  and  he  should  be  addressed: 

SUPERINTENDENT  OP  DOCUMENTS, 

Government  Printing  Office, 

Washington,  D.  C. 

The  general  law  under  which  publications  are  distributed  prohibits  the  giving  of 
more  than  one  copy  of  a  publication  to  one  person.  The  cost  of  this  publication  is  5 
cents. 

First  edition.     June,  1915. 


Geology 
Library 

TN 


M7KG 
CONTENTS. 


Page. 

Introduction 5 

Properties  of  monazite 5 

Occurrence  of  monazite '. 6 

Where  monazite  is  mined 6 

History  of  production  of  monazite 7 

First  German  thorium  convention 7 

Second  German  thorium  convention 8 

Causes  of  reduced  price  of  thorium 9 

Consumption  of  monazite 9 

Prospecting  for  monazite  deposits 10 

Use  of  spectroscope 10 

Monazite  deposits  in  North  and  South  Carolina 10 

North  Carolina 11 

South  Carolina 12 

Deposits  in  Idaho  and  Colorado '. . . .  12 

Idaho 12 

Colorado 13 

Deposits  in  Brazil 13 

Mining  of  monazite  in  the  Carolinas , 14 

Milling  methods  in  the  Carolinas 16 

Electromagnetic  equipment  used J  6 

By-product  separation .' 17 

Cost  of  mining  and  milling 17 

Comments  on  electromagnetic  process 18 

Estimated  monazite  resources 19 

Duty  on  monazite  exported  from  United  States  and  Brazil 20 

United  States 20 

Brazil 20 

Import  duties  on  monazite 20 

Examination  and  valuation  of  monazite  deposits 20 

Attempts  to  use  by-products 22 

Method  for  the  determination  of  thorium  in  monazite 23 

Treatment  of  monazite  for  the  extraction  of  thorium 24 

Separation  of  mesothorium  on  a  commercial  scale 25 

Quantitative  determination  of  mesothorium 2(5 

Minerals  in  monazite  sands 27 

Flow  sheet 2? 

Selected  bibliography 30 

Publications  on  mineral  technology 31 


ILLUSTRATION. 


FIGURE  1.  Flow  sheet,  shdwlng  steps  in  process  of  magnetic  separation  of 

monazite  sands 

3 


MONAZITE,  THORIUM,  AND  MESOTHORIUM. 


By  KARL,  L.  KITHIL. 


INTRODUCTION. 

The  monazite  industry  in  the  United  States  has  been  practically  at 
a  standstill  since  1906,  principally  for  the  reason  that  monazite  could 
he  mined  and  obtained  cheaper  from  Brazil,  where  large  deposits  are 
found  and  exploited  along  the  seacoast  and  in  the  interior.  For- 
merly part  of  the  monazite  mined  in  the  States  of  North  and  South 
Carolina  was  used  for  the  manufacture  of  thorium  nitrate  in  this 
country  and  part  of  the  production  was  sent  to  Germany.  It  seems 
an  opportune  time  to  call  attention  to  the  monazite  deposits  in  the 
United  States,  as  the  imports  of  thorium  nitrate  are  at  present  cur- 
tailed. There  is  reason  to  believe  that  a  more  general  manufacture  of 
thorium  nitrate  may  be  developed  in  this  country.  It  may  be  many 
years  before  supplies  of  the  nitrate  from  Europe  can  be  depended 
upon. 

There  are  deposits  of  monazite  in  several  of  our  States,  and  with 
the  knowledge  that  a  valuable  product — mesothorium — can  be  made 
as  a  by-product  from  the  residues  of  thorium  nitrate  manufacture  the 
industry  may  be  developed  in  this  country  and  should  pay  well. 
Mesothorium  is  used  successfully  in  therapy  in  the  same  manner  as 
radium. 

With  these  facts  in  view  the  following  description  of  the  occurrences 
of  monazite  in  the  United  States,  the  uses  to  which  its  products  can 
be  put,  and  the  methods  of  mining  and  treatment  has  been  prepared 
by  the  Bureau  of  Mines  with  the  purpose  of  aiding  more  efficient 
utilization  of  radioactive  minerals. 

PROPERTIES  OF  MONAZITE. 

Monazite  is  an  anhydrous  phosphate  of  the  rare  earths,  especially 
cerium,  lanthanum,  neodymium,  praseodymium,  yttrium,  and 
erbium,  and  contains  also  a  small  percentage  of  thorium.  So  far  its 
content  of  thoria  only  gives  the  mineral  its  commercial  importance, 
although  a  market  is  being  developed  for  some  of  the  other  rare 
earths  in  special  types  of  electrodes  for  arc  lamps  and  in  the  flaming 
arc.  The  content  of  thoria  in  monazite  is  small  and  varies  from  a 
fraction  of  1  per  cent  to  about  12  per  cent,  although  monazite  con- 
taining less  than  3£  per  cent  of  ThO2  can  not  be  used  successfully  in 

5 


1019019 


6  MONAZITE,   THORIUM,   AND   MESOTHORIUM. 

the  manufacture  of  thorium  nitrate,  which  is  the  important  chemical 
product  necessary  for  the  manufacture  of  incandescent  gas  mantles. 
In  this  manufacture  the  thorium  is  mixed  with  1  to  2  per  cent  of  other 
nitrates  of  the  rare  earths.  References  to  the  percentage  of  thoria  in 
"monazite"  generally  apply  to  a  sand  containing  about  92  to  95  per 
cent  of  true  monazite;  such  sand  is  sold  in  the  market  on  the  basis  of 
its  content  of  thoria  at  a  fixed  price  per  unit. 

Monazite  possesses  radioactive  properties  strong  enough  to  affect 
a  photographic  plate  and  to  be  measured  in  the  electroscope.  The 
activity  of  the  sand  is  due  to  its  content  of  mesothorium  and  radium. 

The  specific  gravity  of  monazite  varies  from  4.9  to  5.3.  It  has  a 
hardness  of  5,  is  somewhat  brittle,  and  can  be  easily  pulverized. 

Nearly  all  of  the  monazite  brought  to  the  market  is  of  a  yellowish, 
resinous  color.  The  Brazilian  monazite  of  the  coast  lands  appears  to 
have  a  more  uniform  shade  of  color  and  size  of  grain  than  the  mona- 
zite from  the  interior.  The  region  from  which  monazite  from  the 
Carolinas  has  been  mined  can  often  be  determined  by  its  color  alone. 
Carolinian  monazite  ranges  from  yellowish  to  brownish,  greenish  and 

grayish  in  color. 

OCCURRENCE  OF  MONAZITE. 

Monazite  is  usually  found  in  the  gravel  of  small  streams  or  bottom 
lands,  but  sometimes  it  is  also  found  in  the  soil  of  hillsides.  In  Brazil 
it  occurs  also  in  the  beach  sands  of  the  coast.  In  places  it  is  found  in 
small  crystals  in  gneiss,  granite,  and  pegmatite  (crystalline)  rocks. 

As  these  rocks  become  disintegrated,  the  crystals  are  washed  into 
the  creeks  and  streams  _and,  together  with  other  heavy  sands,  are 
deposited  in  the  beds  of  such  watercourses.  They  are  thus  concen- 
trated in  the  gravel  by  the  natural  flow  of  the  water;  the  lighter 
clay  and  quartz  sand  being  carried  away.  On  the  coast  of  Brazil  the 
monazite  from  the  crystalline  rocks  of  the  coastal  mountains  is  con- 
centrated in  strata  by  the  waves  of  the  sea.  The  mountain  sides  are 
washed  down  by  the  strong  waves  at  high  tide  and  during  storms. 

In  some  places,  especially  Norway,  monazite  is  imbedded  in  thin 
layers  of  mica  (biotite)  in  strata  or,  in  places,  in  mica  schists.  Such 
monazite  is  usually  of  high  grade  but,  on  account  of  the  enormous 
masses  of  rock  material  that  have  to  be  handled  and  crushed  before 
concentration,  these  deposits  can  not  be  considered  of  commercial 
importance.  The  proportion  of  monazite  in  these  rocks  averages 
perhaps  0.01  per  cent. 

WHERE  MONAZITE  IS  MINED. 

Monazite  has  thus  far  been  mined  successfully  only  in  North  and 
South  America — 'in  North  America,  in  the  Carolinas  and  in  Idaho, 
and  in  South  America  in  Brazil.  The  Brazil  deposits  occur  along 
the  coast  of  the  States  of  Bahia  and  Espirito  Santo,  and  also  less 


HISTORY   OF   PRODUCTION   OF   MONAZITE.  7 

abundantly  on  the  Parahyba  River  in  the  States  of  Eio  de  Janeiro 
and  Minas  Geraes.  Other  coastal  lands  in  the  State  of  Rio  de 
Janeiro  have  also  been  worked.  Deposits  of  monazite  sand  have 
been  found,  too,  in  Swaziland,  Africa,  as  well  as  in  Ceylon  and  in 
Australia.  In  Jekaterinburg,  Russia,  it  occurs  in  native  rock  and 
placers.  It  has  also  been  exported  from  Trovancore,  India. 

In  the  United  States,  occurrences  of  monazite  are  known  in  many 
other  States  than  the  Carolinas,  but  it  is  probable  that  the  deposits 
in  Idaho  and  the  Carolinas  alone  are  of  importance  commercially. 

Brazil  has  furnished  the  bulk  of  monazite  for  commercial  use. 
Little  has  been  mined  elsewhere  since  the  enormous  price  cut  in  the 
earlier  part  of  1906,  as  the  workings  in  the  Carolinas  have  been 
gradually  abandoned.  For  some  years  past  Brazil  has  furnished  all 
of  the  monazite  for  the  gas-mantle  industry  for  both  Europe  and  the 
United  States. 

HISTORY  OF  PRODUCTION  OF  MONAZITE. 

Although  generally  known  to  interested  persons,  a  short  history 
of  the  development  of  production  and  final  overproduction  of  this 
once  rare  mineral  may  be  warranted. 

The  first  monazite  used  in  Europe  for  chemical  purposes  was 
brought  at  great  expense  from  Sweden  and  Norway. 

About  27  years  ago  John  Gordon,  an  American,  found  monazite 
on  the  coast  of  Brazil,  in  the  State  of  Bahia,  and  brought  the  mineral 
in  large  quantities  to  Hamburg.  The  supply  was  sufficient  to  furnish 
the  thorium  industry  of  the  entire  world  with  monazite  at  a  com- 
paratively low  price.  Mr.  Gordon  obtained  a  monopoly  of  the  Bahian 
monazite  sands. 

At  that  time  the  manufacture  of  thorium  nitrate  in  Europe  as  a 
specialty  was  confined  to  a  few  large  chemical  firms  in  Germany  and 
to  the  Welsbach  Co.  in  Vienna.  These  were  the  only  firms  that 
provided  the  European  market  with  thorium  nitrate.  They  also 
sent  large  quantities  of  the  nitrate  to  the  United  States.  The 
American  Welsbach  Co.  early  manufactured  thorium  nitrate  from 
sands  mined  in  the  Carolinas,  a  protective  duty  of  6  cents  per  pound 
making  this  possible,  as  the  mining  of  monazite  in  this  country  is 
more  expensive  than  in  Brazil. 

FIRST   GERMAN    THORIUM    CONVENTION. 

Late  in  1902  Mr.  Gordon  entered  into  an  agreement  with  the  four 
largest  German  manufacturers  and  with  the  Austrian  manufacturer 
by  which  he  agreed  to  furnish  monazite  at  a  price  of  $150  per  metric 
ton  and  a  percentage  of  the  profits  from  the  manufactured  nitrates. 
With  this  agreement  a  close  combination  was  formed  which  prevented 
other  thorium  manufacturers  from  acquiring  any  of  the  mineral 


8  MONAZITE,   THORIUM,  AND   MESOTHOBIUM. 

mined  by  Mr.  Gordon.  The  combination  was  known  as  the  German 
Thorium  Convention,  which,  after  the  conclusion  of  the  agreement 
with  Mr.  Gordon,  immediately  raised  the  price  of  thorium  nitrate 
100  per  cent. 

Mr.  Gordon's  supply  came  from  the  coast  lands  of  Bahia,  near 
Prado,  Brazil,  and  he  exported  the  sands  for  a  long  period  without 
interference.  Finally  the  Brazilian  Government  became  acquainted 
with  the  value  of  the  resources  and  found  an  old  law  according  to 
which  all  of  the  Brazilian  coast  lands  along  the  sea  and  navigable 
rivers  belong  exclusively  to  the  Federal  Government  for  defensive 
purposes.  The  Government  concluded,  therefore,  that  no  private 
individual  or  State  government  had  the  right  to  mine,  sell,  lease,  or 
remove  any  of  this  property  without  the  consent  of  Federal  authority. 
In  1903  the  Government  of  Brazil  advertised  that  coast  lands  in  the 
State  of  Espirito  Santo  would  be  leased  to  the  highest  bidder  for  the 
exploitation  of  the  sands  lying  within  its  territory. 

A  business  man  living  in  Rio  de  Janeiro  made  a  contract  with  the 
Government,  but  for  some  reason  allowed  it  to  lapse.  Finally  an 
engineer  obtained  the  contract  for  the  firm  of  A.  C.  de  Freitas  &  Co., 
of  Hamburg,  Germany.  By  the  contract  the  firm  mentioned  agreed 
to  pay  to  the  Brazilian  Government  a  rental  of  50  per  cent  of  the 
selling  price  of  monazite  sand  and  to  export  at  least  1 ,200  tons  annu- 
ally during  the  life  of  the  contract. 

SECOND    GERMAN    THORIUM    CONVENTION. 

To  avoid  interference,  the  German  Thorium  Convention  arranged, 
later  on,  that  half  of  its  supply  should  be  furnished  by  Mr.  Gordon 
and  half  by  the  De  Freitas  Company;  and  a  new  convention  was 
formed  by  the  four  German  chemical  manufacturers  with  Mr.  Gordon 
and  the  De  Freitas  Company  by  which  the  latter  two  were  to  supply 
the  monazite  to  the  four  German  manufacturers  only  and  were  to 
receive  therefor  $150  per  ton  of  monazite  and  a  percentage  of  the 
profits  from  the  sale  of  the  nitrates. 

As  a  result  of  the  convention  other  firms  in  various  countries,  which 
had  in  the  meantime  begun  to  manufacture  thorium  nitrate,  were 
without  a  supply  of  raw  material  and  had  to  depend  upon  the  ashes 
of  spent  mantles.  Consequently,  they  made  every  effort  to  find  and 
develop  new  deposits  of  monazite  in  Brazil,  the  Carolinas,  and  else- 
where. The  whole  world  was  searched  for  rare-earth  minerals  by 
their  engineers,  with  the  interest  and  assistance  of  many  governments. 
The  high  price  for  thorium  nitrate  made  it  possible  to  mine  monazite 
hi  the  Carolinas  and  export  it  to  Germany;  thus  one  German  manu- 
facturer— an  outsider — received  his  supply  from  North  and  South 
Carolina.  Later,  American  firms  independent  of  the  Welsbach  com- 


HISTORY    OF    PRODUCTION    OF    MONAZITE.  9 

panies  began  to  buy  monazite  in  the  Carolinas,  and  by  the  compe- 
tition created  for  a  brief  period  caused  the  price  for  lands  and  monazite 
sand  to  rise  to  a  point  highly  profitable  to  the  farmers  and  landowners 
of  the  Carolinas. 

CAUSES    OF    REDUCED    PRICE    OF    THORIUM. 

On  account  of  overproduction  in  thorium,  the  price  for  thorium 
nitrate  was  suddenly  dropped  50  per  cent  by  the  convention  in  the 
year  1906.  The  mining  of  monazite  consequently  decreased  in  all 
localities  where  the  cost  of  the  mining  was  high,  as,  for  instance,  in. 
the  Carolinas. 

Since  1906  other  difficulties  have  arisen  between  the  Vienna  and 
English  Welsbach  companies  and  the  German  Thorium  Convention; 
and  in  1910  the  price  was  further  lowered  to  a  point  that  made  the 
mining  of  monazite  absolutely  unprofitable  in  the  Carolinas,  and  also 
in  the  interior  of  Brazil.  The  market  was  flooded  with  monazite 
until  the  outbreak  of  the  European  war. 

The  German  Incandescent  Gas  Light  Co.  of  Berlin  has  succeeded 
during  the  past  few  years  in  controlling  the  largest  manufacturers  of 
thorium  nitrate  in  Europe  with  the  exception  of  those  in  France. 
The  German  concern  controls  now  both  the  English  and  Austrian 
Welsbach  companies,  and  consequently  their  thorium  nitrate  plant 
in  Austria.  This  combination  is  the  strongest  competitor  of  the  so- 
called  Thorium  Convention,  and  the  latter  has  lost  much  of  its  power. 

CONSUMPTION    OF   MONAZITE. 

The  world's  consumption  of  monazite  is  now  about  3,000  tons  per 
annum.  The  annual  world  consumption  of  incandescent  gas  mantles 
is  estimated  at  three  hundred  million.  The  United  States  alone,  in 
spite  of  the  development  and  use  of  the  electric  metal-filament  lamps, 
has  consumed  in  the  past  few  years  some  eighty  million  incandescent 
gas  mantles  as  against  forty  million  total  before  the  year  1904. 

In  the  manufacture  of  such  gas  mantles  about  0.5  gram  of  ThO2, 
equal  to  1  gram  of  thorium  nitrate,  is  used  per  mantle;  hence,  the 
world  consumption  of  thorium  nitrate  is  300,000  kilos,  equal  to 
150,000  kilos  of  ThO2  per  annum.  If  monazite  is  considered  to 
contain  5  per  cent  ThO2,  with  a  90  per  cent  recovery  in  the  manufac- 
ture, 1,000  kilos  (1  metric  ton)  of  monazite  will  yield  90  kilos  of 
thorium  nitrate.  The  gas  mantles  are  made  of  99  per  cent  thorium 
and  1  per  cent  cerium. 

Perhaps  the  best  work  in  regard  to  the  manufacture  of  thorium 
nitrate  and  incandescent  gas  mantles  has  been  written  by  Bohrn.0 

oBohm,  Richard,  Das  Gasgluehlicht,  Die  Fabrication  der  Gluehkoerper  fuer  Oasgluehlicht,  Leipsic 
1905;  Die  Thorium  Industrie:  Chem.  Ind.,  vol.  9,  1906,  vol.  29,  pp.  450-488. 

93290°— 15 -2 


10  MONAZITE,    THORIUM,   AND   MESOTHORIUM. 

PROSPECTING  FOR  MONAZITE  DEPOSITS. 

Prospecting  for  monazite  is  similar  to  a  search  for  gold.  The 
mining  pan  of  the  batea  is  the  most  convenient  apparatus  in  which 
to  wash  the  gravels  of  the  streams  and  separate  the  heavier  sands,  from 
among  which  monazite  can  be  easily  detected  by  its  peculiar  luster 
and  color.  Sounding  rods  should  be  employed  if  quick  estimates 
are  desirable  and  if  the  thickness  and  composition  of  the  overlying 
burden  in  the  bottom  lands  must  be  established.  The  concentrated 
material  of  the  pannings  is  dried  and  sent  to  the  chemical  laboratory 
for  determination  of  the  content  of  thoria  and  other  rare  earths. 

USE   OF   SPECTROSCOPE. 

It  probably  is  not  widely  known  that  the  presence  of  some  of  the 
rare  earths  in  monazite  can  be  easily  detected  by  the  aid  of  a  spec- 
troscope, a  pocket  or  hand  spectroscope  being  sufficient.  Peculiar 
as  it  may  seem,  the  presence  of  rare  earths  in  the  monazite  samples 
as  taken  from  the  pan  can  be  at  once  determined  by  this  method. 
Determination  is  best  accomplished  by  spreading  some  of  the  con- 
centrated sand  on  a  piece  of  paper  or  cloth  and  holding  the  spectro- 
scope over  the.  sand  at  a  convenient  angle,  the  natural  light  falling 
directly  on  the  sand.  A  f  airly  broad  dark  line  will  appear  between  the 
red  and  the  yellow  of  the  spectrum,  and  another  but  narrower  line 
will  be  seen  in  the  green.  These  dark  absorption  bands  seem  to  be 
due  principally  to  the  presence  of  the  rare-earth  oxides  of  neodymium, 
praseodymium,  and  erbium  contained  in  the  mineral.  Such  spec- 
trum tests  for  monazite  can  be  safely  relied  upon  when  observed  by 
the  trained  eye.  The  entire  spectrum  used  is  divided  into  a  scale 
of  63  mm.,  the  first  and  broader  dark  line  becoming  visible  between 
the  13  and  15  mm.  lines.  The  narrow  dark  line  appears  between  21 
and  22  mm.  of  the  scale. 

The  spectrum  method  of  testing  in  the  field  is  most  helpful  in  fara- 
way places  where  a  laboratory  is  not  available. 

MONAZITE  DEPOSITS  IN  NORTH  AND  SOUTH  CAROLINA. 

The  monazite  deposits  in  the  Carolinas  cover  an  area  of  several 
hundred  square  miles  east  of  the  Blue  Ridge  Mountains  and  extend 
in  a  southwest  direction.  In  North  Carolina  the  counties  of  Cleve- 
land, Burke,  Alexander,  Rutherford,  and  Lincoln  furnish  the  richest 
deposits.  In  South  Carolina  the  only  deposits  of  value  are  in  the 
counties  of  Cherokee  and  Greenville. 

Practically  all  of  the  monazite  mined  in  the  Carolinas  is  derived 
from  the  gravels  in  the  streams  and  bottom  lands,  the  miner  usually 
following  the  old  courses  of  the  streams  and  creeks  in  the  bottoms. 
The  gravels  are  of  greatly  varying  thickness  throughout,  and  it  is, 
therefore,  difficult  to  arrive  at  a  true  estimate  for  an  average  value. 


MONAZLTE    DEPOSITS  IN    NORTH   AND   SOUTH    CAROLINA.  11 

From  experience,  however,  it  can  be  estimated  that  an  average  thick- 
ness of  the  monazite-bearing  gravels  is  between  1£  and  2£  feet.  There 
are  deposits  with  a  thickness  of  3  feet  and  more,  but  they  are  of  rare 
occurrence.  The  top  soil  in  the  bottom  lands  varies  on  an  average 
from  3  to  6  feet,  and  on  the  outer  seams  of  the  bottom  toward  the 
hillsides  frequently  increases  to  a  thickness  of  7  feet  or  more.  The 
top  soil  is  barren  and  consists  usually  of  sandy  soil  interlined  with 
clays,  or  is  of  clayey  matter  throughout.  Hydraulic  methods  have 
been  tried  on  some  of  the  richer  soil  deposits,  but  without  much 
success. 

NORTH    CAROLINA. 

In  North  Carolina  deposits  of  monazite  sand  are  found  in  Burke 
County  in  the  Brindletown  district.  Here  monazite  is  obtained  from 
the  hydraulic  washings  of  the  gold  placers.  The  content  of  monazite 
in  the  concentrated  black  sands,  however,  is  small  compared  with  that 
of  the  sluicing  concentrates  of  other  sections.  The  monazite  in  this 
section  after  being  purified  seldom  shows  a  higher  content  than  3.5  to 
3.75  per  cent  ThO2.  There  is  considerable  magnetite  in  these  sands, 
and  the  bulk  of  the  concentrates  consists  of  ilmenite  (titanif erous  iron) . 

McDowell  County  has  a  number  of  deposits  in  the  vicinity  of 
Muddy  Creek.  The  occurrence  of  monazite  here  is  closely  similar 
to  that  of  Brindletown,  but  perhaps  contains  less  gold  in  the  sand. 

In  Rutherford  County,  within  a  few  miles  of  Rutherfordton,  there 
are  a  number  of  deposits  that  have  been  profitably  worked  for  some 
time  for  both  gold  and  monazite.  The  gold  has  usually  been  extracted 
by  the  miner  and  the  residues  further  concentrated  and  shipped  for 
their  content  of  monazite.  This  district  is  especially  interesting  on 
account  of  the  large  area  of  the  wide  bottom  lands  where  the  gravel 
bearing  monazite  and  gold  is  found  to  a  greater  extent  than  in  most 
other  sections.  The  percentage  of  monazite  in  the  gravel,  however,  is 
not  large,  and  these  lands  have  been  worked  profitably  only  on  account 
of  their  gold  content,  the  monazite  being  obtained  as  a  by-product. 

Much  activity  was  shown  years  ago  in  the  vicinity  of  Ellenboro, 
extending  to  Oak  Spring  and  Sandy  Run  Creek  and  up  as  far  as 
Duncan,  which  is  about  18  miles  from  Ellenboro.  The  deposits  in 
this  region  are  more  or  less  alike  and  the  monazite  obtained  is  of  good 
grade  and  can  still  furnish  considerable  quantities  of  concentrates. 
Near  Ellenboro  is  a  hillside  deposit  in  which  monazite  is  found  in  a 
comparatively  pure  state  in  the  sand  of  the  hillside  as  well  as  in  the 
gravels  of  the  bottom  lands. 

Cleveland  County  has  a  considerable  area  of  riionazite-bea>ring 
gravels  which  extends  between  Shelby  and  Mooresboro  via  Fallston 
to  a  place  called  Zite  near  Carpenters  Knob,  a  well-known  peak  in  that 
section.  The  deposits  around  Fallston  and  in  the  entire  Carpenters 
Knob  region  are  of  great  importance  and  have  furnished  monazite 


12  MONAZITE,    THORIUM,   AND   MESOTHOBIUM. 

concentrates  of  especially  high  thorium  content.  The  rough  concen- 
trates obtained  from  many  of  the  streams  in  that  region  contain  less 
black  sand  and  garnets  than  those  in  most  other  sections. 

There  are  also  fair  deposits  in  Lincoln  County  about  15  miles  north- 
west of  Lincolnton.  These  deposits  can  also  be  reached  from  Shelby, 
N.C. 

Alexander  County  has  furnished  some  monazite  concentrates,  and 
there  is  no  doubt  but  that  other  deposits  can  be  found  in  that  county. 

There  has  been  in  former  years  considerable  activity  also  near  Hil- 
debran,  Burke  County,  where  fair  deposits  of  considerable  extent  have 
been  found. 

SOUTH    CAROLINA. 

Nearly  all  the  monazite-bearing  gravel  in  South  Carolina  is  found 
north  of  Gaffney,  Cherokee  County,  and  Cowpens,  Spartanburg 
County,  and  in  the  vicinity  of  Greenville,  Greenville  County,  south 
of  the  Southern  Railway. 

There  is  a  considerable  area  of  monazite  found  in  the  gravels  of 
the  creeks  and  bottoms  in  all  of  these  sections,  and  although  there 
have  been  obtained  considerable  quantities  of  monazite  concentrates 
containing  30  to  40  per  cent  of  monazite,  the  bulk  of  the  crude  con- 
centrates coming  from  these  South  Carolina  sections  have  been  of 
the  "black-sand"  variety  containing  considerable  ilmenite. 

Many  of  these  deposits  in  both  North  and  South  Carolina  have 
been  described  by  others,  and  the  reader  is  referred  to  the  bibli- 
ography at  the  end  of  this  report. 

DEPOSITS  IN  IDAHO  AND  COLORADO. 


The  Idaho  monazite  deposits  and  the  treatment  of  the  gold- 
monazite-bearing  sands  in  that  State  have  been  well  described  by 
Sterrett,0  also  by  Schrader,6  and  the  concentration  methods  for  the 
monazite  sand  used  in  Idaho  are  mentioned  in  the  report  of  the 
Idaho  inspector  of  mines  for  1910. 

The  monazite  deposits  near  Centerville  and  Idaho  City,  Idaho, 
seem  to  be  of  especial  importance.  There  is  no  doubt  but  that  con- 
siderable monazite  will  be  found  in  many  places  in  the  State  and  all  the 
gravels  of  the  deposits  contain  a  considerable  amount  of  gold  which 
makes  possible  the  working  of  such  deposits  for  both  gold  and 
monazite.  The  gravel  beds  are  considerably  thicker  than  those  in 
the  Carolinas,  and  much  monazite  should  be  obtained  from  the 
tailings  from  the  old  gold  washings.  It  must  be  remembered,  how- 
ever, that  the  wages  paid  to  the  miners  in  Idaho  are  considerably 
higher  than  those  paid  in  the  Carolinas. 

«  Sterrett,  D.  B.,  Monazite  in  Idaho:  U.  S.  Geol.  Survey  Mineral  Resources,  1909,  pp.  898-903,  1910. 
*  Schrader,  F.  C.,  An  occurrence  of  monazite  in  northern  Idaho:  IT.  S.  Geol.  Survey  Bull.  430, 1910,  p.  184. 


DEPOSITS   IN    BRAZIL.  13 

COLORADO. 

Monazite  has  been  found  in  thg  State  of  Colorado  some  20  miles 
south  of  Denver  in  the  Newlands  Gulch  district,  where  the  monazite 
occurs  in  some  of  the  gravels,  which  carry  also  considerable  gold. 
Monazite  is  also  reported  in  the  Platte  Canyon. 

DEPOSITS  IN  BRAZIL. 

There  are  three  kinds  of  deposits  of  monazitic  sands  found  in 
Brazil,  as  follows: 

1.  Deposits  within  the  marinhas  (Government  lands). 

2.  Deposits  lying  behind   the  marinhas  that  are  private  State 
possessions  or  belong  to  private  parties. 

3.  Inland  deposits. 

The  marinhas  extend  from  points  in  the  State  of  Rio  de  Janeiro 
north  through  the  State  of  Espirito  Santo  into  the  State  of  Bahia. 

The  bulk  of  the  monazite  is  derived  from  these  coast  sands  in  the 
States  of  Espirito  Santo  and  Bahia.  The  monazite  sand  at  some 
places  could  in  former  years  be  taken  off  the  beach  by  skimming  the 
surface  after  each  tide,  and  was  pure  enough  to  be  shipped.in  the  crude 
state.  In  later  years,  however,  the  material  has  been  of  consider- 
ably lower  grade,  so  that  oscillating  tables  have  been  employed,  and 
some  of  the  sands  have  been  washed  in  sluice  boxes  wherever  enough 
fresh  water  was  obtainable.  The  sluice  boxes  used  are  larger  and 
of  a  different  construction  than  in  the  Carolinas,  and  no  perforated 
plate  is  necessary,  as  there  is  no  coarse  gravel  in  the  beach  sands. 
Electromagnetic  separators  have  also  been  used  direct.  These 
coast  lands,  called  "marinhas,"  are  the  property  of  the  Federal 
Government  for  33  meters  inland,  measured  from  the  point  where 
the  sea  waters  wash  the  beach  at  mean  high  tide.  This  method  of 
marking  property  is  uncertain,  and  has,  of  course,  given  rise  to  dis- 
putes when  boundaries  are  established. 

At  a  few  places  along  the  coast  are  strips  of  monazite-bearing  sands, 
lying  directly  behind  or  not  far  from  the  so-called  marinhas,  and  some 
of  these  could  be  worked  profitably  were  it  not  for  the  difficulties 
of  proving  to  the  Federal  Government  that  these  sands  were  not  taken 
from  the  near-by  marinhas.  One  French  concern  is  exploiting  such 
lands  near  Itabapoana,  in  the  State  of  Rio  de  Janeiro,  and  has 
exported  several  hundred  tons  of  the  mineral  annually  for  some  years. 
There  are  several  other  deposits  that  could  be  worked,  situated 
between  Gargahu  and  Itabapoana;  but,  owing  to  political  influences, 
no  other  concerns  have  thus  far  been  able  to  obtain  concessions. 

In  the  interior  of  Brazil,  monazite  occurs  in  many  places,  but  a 
fuller  description  of  the  localities  and  deposits  will  not  be  given  here. 

The  deposits  of  monazite  in  the  interior  of  Brazil  are  of  a  formation 
similar  to  those  in  the  Carolinas,  the  small  streams  and  bottom  lands 


14  MONAZITE,   THORIUM,   AND  MESOTHORIUM.  • 

containing  the  only  deposits  of  sands  possessing  commercial  impor- 
tance. 

The  contents  of  monazite  in  the  gravels  of  the  streams  and  bottom 
lands  averages  about  0.25  to  0.3  per  cent,  a  proportion  about  the 
same  as  that  in  the  monazite  in  the  Carolinas.  There  are  richer 
deposits,  however,  in  several  sections. 

Along  the  banks  of  larger  rivers,  as,  for  instance,  the  Parahyba, 
great  quantities  of  black  sands  with  traces  of  monazite  are  found. 
Near  Sapucaia,  opposite  Benjamin  Constant  Station  on  the  Central 
Railway,  such  deposits  have  been  worked  by  a  French  concern.  They 
finally  had  to  stop  work  at  this  point  and  abandon  also  their  openings 
hi  the  mountainous  part  of  this  region. 

Many  of  the  inland  deposits  can  not  be  exploited  on  account  of  the 
expense  of  transportation  of  the  product,  the  deposits  being  situated 
many  miles  from  the  railroad  and  the  roads  and  trails  being  in  such 
condition  that  it  is  often  difficult  to  travel  over  them  even  with  the 
mule  caraven  (troupa).  The  soft  clays  in  the  thickets  of  the  jungle- 
like  forests  and  the  crossing  of  swamps  make  travel  in  many  cases 
almost  impossible,  especially  with  a  heavy  burden  laden  on  the  mule's 
back.  The  rivers  in  most  sections  are  not  yet  navigable.  Frequent 
floods,  caused  by  heavy  tropical  rains,  and  the  lack  of  proper  labor 
make  difficult  continuous  operation  in  the  interior  of  Brazil. 

At  the  present  prices  of  thorium  nitrate  such  lands  in  the  interior 
can  not  be  profitably  exploited  by  any  known  method.  When  once 
the  large  deposits  along  the  coast  are  exhausted,  however,  and 
the  price  for  thorium  rises,  or  if  some  other  uses  for  the  mineral  and 
its  rare-earth  contents  are  discovered,  then  these  deposits  may 
become  available. 

MINING  OF  MONAZITE  IN  THE  CAROLINAS. 

Most  of  the  mining  for  monazite  in  the  Carolinas  is  carried  out  in 
a  primitive  way,  similar  to  the  old  methods  of  gold  mining.  The 
gravel  is  washed  in  sluice  boxes  without  riffles,  the  sands  being  stirred 
with  a  square  shovel,  with  an  upward  movement  toward  the  head  of 
the  sluice  box,  the  sands  of  higher  specific  gravity  being  thus  concen- 
trated, whereas  the  lighter  clay  and  some  of  the  quartz  sand  are 
washed  away.  The  gravel  dug  from  the  pit  is  thrown  on  a  perforated 
plate,  which  is  fastened  over  the  head  of  the  sluice  box.  The  larger 
stones  are  removed  from  the  plate.  A  stream  of  water  (about  18  to 
20  gallons  per  minute)  is  fed  through  a  spout  to  the  gravel  on  the 
screen,  and  the  sand  is  washed  through  the  holes,  about  one-eighth 
of  an  inch  in  diameter,  in  the  plate  into  the  head  of  the  box.  Usu- 
ally two  men  are  employed  to  each  sluice  box,  one  digging  and  lifting 
the  gravel  out  of  the  pit  to  the  screen  and  the  other  concentrating  the 
sand  by  stirring  it  in  the  box  with  the  motion  described  above.  With 


MINING    OP    MONAZITE   IN    THE   CAROLINAS.  15 

this  method  much  of  the  finer  sand  is  lost,  as  the  grains  of  sand  vary 
greatly  in  size,  and  the  finer,  heavier  grains  of  monazite  are  carried 
away  by  mechanical  action  with  the  lighter  and  coarser  quartz.  If 
the  sands  are  properly  sized  before  being  washed,  a  much  better 
result  can  be  obtained,  and  practically  all  of  the  monazite  contained 
in  the  gravel  or  sand  can  thus  be  saved. 

The  sluice  boxes  are  of  such  construction  that  easy  transportation 
is  possible,  a  desirable  feature,  because,  as  the  gravel  is  worked  out 
in  one  pit  in  one  or  two  days'  time,  the  boxes  then  have  to  be  moved 
higher  up  the  stream  or  bottom.  It  has  been  found  more  practical 
and  cheaper  to  remove  the  box  to  the  deposit  than  to  bring  the  gravel 
to  the  box.  The  sluice  box  is  usually  brought  over  the  pit,  which 
has  been  worked  out  previous  to  the  removal  of  the  box,  thereby 
furnishing,  to  some  extent,  a  dumping  place  for  the  tailings  that  flow 
off  the  end  of  the  sluice  box.  However,  as  the  amount  of  tailings 
washed  out  during  one  day  is  large,  the  so-called  "tail-raise"  must 
be  cleaned  out  with  the  shovel  several  times  during  the  day,  the  tail- 
ings so  removed  being  thrown  to  one  side  of  the  bank  of  the  tail- 
raise.  This  is  necessary  in  most  instances,  as  the  lands  slope  only 
slightly,  and  in  some  sections  the  bottoms  and  stream  beds  are  almost 
level. 

After  the  sands  have  been  concentrated  in  the  sluice  box,  the  con- 
centrates are  often  rewashed  by  an  experienced  hand  and  a  further 
amount  of  useless  material  removed.  The  concentrates  are  then 
dried  in  the  sun  or  in  a  form  of  drier — usually  made  of  a  piece  of 
sheet  iron  with  turned-up  edges — a  wood  fire  being  built  underneath. 

Many  of  the  Carolina  mines  could  not  have  been  exploited  had  it 
not  been  for  the  fact  that  the  people  worked  out  the  mineral  on  their 
own  account  from  small  deposits  during  times  when  no  farm  work 
could  be  done.  They  seldom  figured  their  time  of  work,  mined  out 
what  they  could,  and  brought  it  to  the  separating  plants,  where  they 
were  paid  in  cash  at  the  rate  of  about  8  cents  per  pound  of  pure 
monazite  (machine-cleaned  sand).  Others  were  employed  by  some 
of  the  corporations  at  about  80  cents  to  $1.25  per  day  at  the  richer 
mines.  It  was  not  long,  however,  before  new  dealers  arrived  in  the 
Carolinas,  greatly  inspired  by  the  high  prices  which  were  then  paid 
for  the  nitrate,  who,  knowing  little  of  the  trade,  and  with  only  crude 
means  of  judging  the  content  of  monazite  in  the  washed  concentrates, 
paid  12,  15,  and  often  as  high  as  35  cents  per  pound,  based  on  con- 
centrates containing  92  per  cent  monazite.  This  development  caused 
unhealthy  competition,  which  proved  fatal  to  the  farmers  and  small 
operators,  as  they  went  to  large  expense  to  produce  large  quantities 
of  the  sand,  which  they  then  held  for  higher  prices,  but  could  not  sell 
at  all  when  finally  the  market  for  thorium  nitrate  broke.  To-day 
there  is  no  mining  of  monazite  in  the  Carolinas. 


16  MONAZITE,   THORIUM,   AND   MESOTHORIUM. 

MILLING  METHODS  IN  THE  CAROLINAS 

The  deposits  are  too  scattered  and  are  not  extensive  enough  to  make 
practical  or  profitable  the  use  of  sliming  and  oscillating  tables.  Other 
concentrating  apparatus  of  special  design  can  be  utilized,  and  with 
proper  sizing  of  the  material  excellent  results  can  be  obtained  with 
such  machines  and  methods,  as  has  often  been  demonstrated  by  prac- 
tical tests. 

The  concentrates  produced  in  the  sluice  boxes  contain  20  to  60  per 
cent  of  monazite.  An  average  of  about  35  per  cent  can  be  considered 
a  conservative  estimate  as  a  result  of  practical  experience.  The 
concentrates  have  to  be  further  refined,  and  are  best  treated  by 
electromagnetic  separators,  of  which  the  Wetherill-Rowand  type  has 
proved  to  be  the  most  useful  to  the  industry.  The  testing  labora- 
tories of  Krupp  now  use  a  new  type  of  electromagnetic  separator  of 
the  Ullrich  type,  which  treats  the  material  either  "wet"  or  dry..  It 
is  reported  to  have  a  capacity  of  about  2  tons  of  material  per  hour, 
which  is  considerably  larger  than  that  of  any  other  type  of  magnetic 
separator  heretofore  kno'wn.  The  Daggett  separator  has  also  been 
used  successfully  for  this  kind  of  concentration. 

ELECTROMAGNETIC    EQUIPMENT    USED. 

In  the  separation  of  monazite  from  other  minerals  and  its  gangue 
materials,  electromagnetic  methods0  were  found  to  be  most  efficient. 

Weakly  magnetic  bodies  can  be  separated  from  each  other  by  em- 
ploying highly  concentrated  magnetic  fields.  Such  separation  is  made 
possible  on  account  of  the  difference  in  the  magnetic  permeability  of 
different  material.  However,  the  magnetic  permeability  as  a  physical 
property  can  be  fixed  only  for  absolutely  pure  material,  entirely  free 
from  any  admixtures,  as  such  admixtures  of  foreign  matter  influence 
considerably  the  magnetic  relativity  of  the  material  to  be  treated,  and 
it  therefore  can  not  be  applied  as  a  theory  in  the  treatment  of  most 
minerals,  which  always  carry  a  certain  amount  of  impurities.  And 
furthermore,  it  is  impossible  to  bring  different  minerals,  by  known 
methods  of  crushing,  grinding,  etc.,  to  a  uniform  size  and  shape  of 
particles,  as  further  factors,  such  as  amount  tested  and  whether  the 
charge  is  packed  tight  or  loose,  affect  the  results,  and  not  even  com- 
paratively correct  results  can  be  obtained.  Only  practical  tests, 
therefore,  will  satisfactorily  determine  the  best  results  for  ores  and 
minerals,  as  on  most  of  such  electromagnetic  separators  the  magnetic 
power  can  be  controlled  to  the  finest  points  by  means  of  a  rheostat. 
The  intensity  of  the  magnetic  field  must  be  adjusted  for  each  specific 
separation  of  minerals. 

The  large  type  of  Wetherill  separator  has  been  used  hi  the  United 
States  and  in  Brazil  for  the  concentration  of  monazite.  The  separator 

o  See  Gunther,  C.  G.,  Electromagnetic  Ore  Separation,  1909.  See  also  "Bibliography  on  magnetic 
concentration"  in  Richards,  R.  H.,  Ore  dressing,  1909,  vol.  2,  pp.  832-837. 


MILLING   METHODS   IN    THE   CAROLINAS.  17 

has  two  magnets  of  different  sizes,  one  being  nearly  twice  the  size  of 
the  other.  Each  of  these  magnets  has  two  pairs  of  poles,  forming  four 
magnetic  fields  and  permitting  a  separation  of  two  products  with  each 
magnet.  (See  fig.  1,  p.  29.)  The  magnets  are  best  adjusted  so  that 
the  first  pole  of  the  first  magnet  removes  from  the  sand  the  highly 
magnetic  material,  as,  for  instance,  the  magnetite  and  ilmenite;  the 
second  pole  of  the  first  magnet  extracts  the  garnets  and  also  the  finer 
grams  of  ilmenite;  the  third  magnet  (being  the  first  pole  of  the  second 
magnet)  removes  all  of  the  coarser  grains  of  monazite;  and  the  last 
pole  extracts  the  finer  grains  of  monazite.  At  the  end  turn  of  the 
18-inch  rubber  belt  of  the  machine  the  residues  are  then  dropped  into 
a  receptacle.  This  is  best  arranged  in  such  manner  that  the  residues 
are  dropped  from  the  funnel  of  the  receptacle  into  the  feed  box  of  a 
small  oscillating  table,  or  other  suitable  means  for  the  wet  concentra- 
tion of  the  gold  and  zircon,  which  are  often  present  in  small  quantities. 
Some  fine  monazite  escaping  with  the  nonmagnetic  material  may  also 
be  recovered. 

BY-PRODUCT    SEPARATION. 

Sometimes  the  by-products  are  found  to  be  valuable  enough  for 
market,  and  it  is  then  of  advantage  to  make  a  still  finer  separation, 
which  can  be  accomplished  by  employing  a  type  of  separator  with 
three  magnets — giving  six  magnetic  fields — of  three  different  sizes 
and  strengths,  the  last  magnet  being  the  largest  and  strongest.  In 
this  way  the  poles  can  be  adjusted  so  that  each  magnetic  field  attracts 
and  removes  practically  the  entire  amount  of  one  certain  kind  of 
mineral  contained  in  the  sands,  thereby  giving  six  distinct  products, 
besides  all  of  the  nonmagnetic  products,  which  are  separated  at  the 
end  of  the  magnetic  operation  by  running  the  residues  over  an  oscil- 
lating table. 

COST    OF   MINING    AND    MILLING. 

The  deposits  of  monazite  sands  in  the  Carolinas  are,  as  has  been 
previously  stated,  patchy,  and  not  one  single  deposit  is  known  to  be 
large  enough  to  justify  the  erection  of  a  large  washing  and  concen- 
trating plant  at  the  mine  itself.  The 'magnetic  separators  are  best 
placed  at  a  point  on  a  railroad,  and  as  nearly  as  possible  in  a  district 
central  to  many  deposits. 

The  percentage  of  monazite  in  the  gravel  averages  0.25  per  cent. 
It  will  thus  be  seen  that  enormous  quantities  of  crude  material  have 
to  be  handled  in  order  to  obtain  a  ton  of  marketable  material — about 
400  tons  of  gravel  furnishes  1  ton  of  monazite.  In  addition,  the 
quantities  of  barren  overburden  which  must  be  removed  have  to 
be  added.  The  overburden  often  averages  more  than  double  the 
amount  of  gravel  to  be  moved.  No  monazite  in  the  Carolinas  can 
be  mined  by  present  methods  for  less  than  6  to  8  cents  per  pound  of 


18  MONAZITE,   THORIUM,   AND  'MESOTHORIUM. 

monazite  contained  in  the  concentrated  material  as  taken  out  of  the 
sluice  box.  This  means  that  to  the  cost  of  the  mining  must  be  added 
the  cost  of  further  concentration,  sacking,  interest  on  investment, 
amortization  on  plant,  management,  freight,  cartage,  etc. 

One  man  can  dig  and  remove  in  nine  hours  (this  being  the  usual 
working  shift  in  the  Carolinas)  about  9  cubic  yards  of  material,  includ- 
ing top  soil,  barren  sand  and  clay,  and  monazite-b earing  gravel. 

The  wages  paid  are  $1  to  $1.25  a  day.  Therefore  if  we  take  for 
a  rough  calculation  an  area  of  3  square  yards  of  ground  and  a  depth 
of  soil  and  gravel  of  9  feet,  equal  to  27  cubic  yards,  or  about  80,000 
pounds  in  weight,  the  cost  would  be  as  follows: 

For  digging  and  removing  of  barren  material  and  dump,  and  digging 
and  removing  to  sluice  box  of  the  monazite-bearing  gravel,  3  men 
at  $1.25,  1  day  each,  or  $3.75;  for  rough  washing  of  9  cubic  yards 
of  gravel  in  sluice  box,  1  man  1  day,  $1.25;  final  cleaning  up  in  special 
sluice  box  of  rough  concentrates,  $0.50 — a  total  of  $5.25. 

As  the  content  of  monazite  in  gravel  is  0.25  per  cent,  or  about  68 
pounds  of  pure  monazite  in  washed  concentrates,  the  cost  is  about 
7f  cents  per  pound  of  monazite  contained  in  the  washed  concentrates. 

The  cost  of  transportation  to  the  magnetic  separator  varies  accord- 
ing to  the  distance  over  which  the  material  has  to  be  hauled,  and 
averages  about  $4  per  ton  of  monazite  in  concentrates,  making  a  total 
cost  of  $159  per  ton  of  monazite  in  concentrates.  To  this  has  to  be 
added  the  cost  of  drying  of  the  crude  concentrates,  and  of  electro- 
magnetic separation.  When  the  plant  is  running  to  its  full  capacity 
(9-hour  shift),  turning  out  about  3  tons  of  pure  monazite  per  shift, 
$10  for  treatment,  depreciation,  separation,  and  repairs  can  safely 
be  added  to  the  above  amount  per  ton  of  monazite.  The  entire  cost 
of  1  ton  of  machine-separated  monazite,  containing  92  to  95  per  cent 
monazite  and  about  4£  per  cent  ThO2  is,  therefore,  $169  at  the  con- 
centrating plant.  To  this  has  to  be  added  the  cost  of  management, 
commissions,  tolls,  if  any,  loading  on  cars,  and  freight  to  chemical 
plant  or  port. 

COMMENTS    ON    ELECTROMAGNETIC    PROCESS. 

In  concentrating  monazite  sands  by  the  electromagnetic  process, 
it  is  essential  that  great  care  be  taken  throughout  the  entire  operation 
that  the  strength  of  the  current  is  the  same  at  all  times,  as  the  slightest 
variation  will  cause  imperfect  separation.  An  impure  product  and 
much  loss  of  monazite  will  result  unless  this  precaution  is  observed, 
as  the  monazite  will  be  taken  up  by  the  wrong  poles.  This  contin- 
gency is  more  fully  illustrated  below: 

If  the  strength  of  current  be  too  great,  some  of  the  monazite  will  be 
mixed  with  the  valueless  ilmenite  or  garnets;  or,  if  the  amperage  be 
too  low,  ilmenite  or  garnets  will  be  carried  over  to  the  next  following 
pole,  and  will  then  become  mixed  with  the  monazite,  and,  at  the  same 


ESTIMATED    MONAZITE    RESOURCES.  19 

time,  too  many  of  the  liner  grains  of  monazite  will  escape  in  the  tail- 
ings. The  distance  between  pole  magnets  must  be  carefully  adjusted, 
and  the  number  of  amperes  for  each  magnet  regulated  by  rheostats 
for  each  kind  of  sand,  for  every  section  of  the  country,  or  even  when 
from  the  same  section  different  percentages  of  monazite  and  impuri- 
ties are  present.™ 

It  may  be  stated  that  a  better  result  is  obtained  when  the  sands 
are  slightly  roasted  before  magnetic  separation  than  if  they  are 
simply  sun-dried  or  air-dried.  The  difference  is  due  to  the  fact  that 
roasting  renders  the  material  more  magnetic.  It  has  accordingly 
been  found  that  the  proper  adjustment  of  the  amperage  for  magnetic 
separation  is  quite  different  for  sands  that  have  been  sun-dried  than 
for  those  dried  over  the  fire. 

Other  electromagnetic  separators  have  been  used,  operating  on 
similar  principles,  but  did  not  give  as  high  concentrates  in  one  oper- 
ation as  the  Wetherill  type,  although,  perhaps,  the  new  Krupp  sepa- 
rator may  do  so.  However,  some  other  concentrators  have  been  used 
with  fair  results. 

By-products  usually  found  in  the  residues  that  can  be  separated  by 
employing  an  oscillating  table  are  zircon,  rutile,  gold,  and  sometimes 
platinum.  Some  of  the  platinum  is  slightly  magnetic,  and  may  be 
lost  during  this  process  of  separation. 

ESTIMATED  MONAZITE  RESOURCES. 

It  is  difficult  to  give  even  a  rough  estimate  of  the  quantities  of 
monazite  obtainable  in  the  various  countries  where  it  occurs.  From 
close  calculations,  however,  it  is  estimated  that  the  lands  in  the 
marinhas  along  the  sea  coast  of  Brazil  may  yield  from  15,000  to 
20,000  tons  of  pure  monazite.  This  does  not  include  coast  lands 
where  the  deposits  have  been  formed  in  comparatively  short  time. 

In  the  interior  of  Brazil  the  writer  knows  of  about  18,000,000  tons 
of  monazite-bearing  gravel  deposits  which  should  yield  monazite 
containing  4^  per  cent  of  thorium  oxide;  and  it  can  be  estimated  that 
these  gravels  contain  45,000  to  60,000  tons  of  monazite.  No  doubt 
there  will  be  found  many  other  deposits  of  greater  or  less  extent  in 
the  interior  of  Brazil,  but  no  single  deposit  in  the  interior,  so  far  as 
known,  would  warrant  the  erection  of  a  large  plant.  In  sections 
where  several  large  deposits  are  found  together  or  near  each  other  a 
washing  and  concentrating  plant  might  be  profitably  established, 
provided  that  the  price  for  the  monazite  obtained  were  higher  than 
at  present  (May,  1915),  and  especially  if  transportation  facilities  from 
the  interior  to  the  coast  became  better.. 

The  amount  of  purified  monazite  available  in  the  Carolinas  may  be 
conservatively  estimated  at  about  15,000  to  20,000  tons  (4£  per 
cent  ThO2). 

a  See  table  on  page.  28. 


20  -    MONAZITE,   THORIUM,   AND   MESOTHORIUM. 

With  better  methods  of  mining  and  refining  the  moiiazite,  perhaps 
those  deposits  could  be  profitably  exploited  at  the  present  prices  for 
monazite  and  thorium  nitrate,  especially  if  the  mining  of  monazite 
were  carried  on  in  connection  with  the  manufacture  of  thorium  nitrate 
and  inesothorium. 

It  is  known  that  attempts  have  been  made  to  extract  the  monazite 
from  the  native  rock,  but  this  operation  with  even  the  richest  rock 
known — 0.1  to  0.2  per  cent  of  monazite — has  proved  to  be  too  expen- 
sive, and  such  endeavors  have  been  given  up  as  hopeless. 

DUTY  ON  MONAZITE   EXPORTED  FROM  UNITED    STATES  AND 
BRAZIL. 

UNITED    STATES. 

There  is  no  duty  on  monozite  exported  from  the  United  States. 

BRAZIL. 

The  duties  on  monazite  exported  from  Brazil  vary  greatly,  and 
are  as  follows: 

BRAZILIAN  EXPORT  DUTIES. 

Federal  Government. — Duty  on  monazite  from  the  marinhas — 
situated  along  the  entire  coast  and  navigable  rivers  of  Brazil — is 
charged  at  the  rate  of  50  per  cent  ad  valorem,  and  is  fixed  at  £30,  or 
about  $150,  per  ton.  Individual  States  have  fixed  duties,  as  follows: 

Rio  de  Janeiro. — 651000  per  metric  ton  (approximately  $21). 

Espirito  Santo. — 80  per  cent  of  selling  value,  established  to  be 
£25  per  ton.  This  duty  is  varying  and  is  subject  to  reduction  when 
applied  for. 

Minas  Geraes. — 12  per  cent  ad  valorem,  fixed  at  £25  per  ton  and 
25  per  cent  ad  valorem,  fixed  at  £25  per  ton,  plus  £2  specific  duty. 

IMPORT  DUTIES  ON  MONAZITE. 

The  duty  on  monazite  imported  into  the  United  States  has  been 
6  cents  per  pound,  but  was  reduced  to  4  cents  in  1910,  and  is  now 
25  per  cent  ad  valorem. 

The  import  duty  on  mantle  ashes  is  $10  ad  valorem. 

The  import  duty  on  nitrates  has  been  25  per  cent  ad  valorem. 

EXAMINATION  AND  VALUATION  OF  MONAZITE  DEPOSITS. 

The  following  features  should  be  ascertained  in  the  investigation 
of  monazite  deposits  for  exploitation: 

1.  Extent  and  depth  of  the  monazite-bearing  alluvial  deposits, 
sands,  and  gravels  in  river  beds  and  bottoms. 

2.  Amount  and  character  of  barren  overburden  overlying  the  gravel 
or  sand  deposit. 

3.  The  percentage  of  monazite  contained  in  the  raw  material  to 
be  treated. 


EXAMINATION    AND   VALUATION    OF    MONAZITE    DEPOSITS.  21 

4.  Percentage  of  thorium  oxide  contained  in  the  monazite. 

5.  Transportation  facilities  and  cost  of  transportation. 

6.  Water  conditions— rain-fall  throughout    the    year   and  water 
supply  for  concentrating  purposes  and  for  the  boiler. 

7.  Timber  obtainable  on  or  near  property  for  building  use,  fuel, 
etc. 

8.  Depth  and  character  of  bedrock. 

9.  Occurrence  and  character  of  clays. 

10.  Power  available. 

11.  Labor,  also  conditions  for  housing. 

12.  Mining  laws. 

13.  Cost  of  supplies. 

14.  Import  and  export  duties. 

15.  Best-suited  methods  for  exploitation  (concentration,  etc.) 

16.  Quantities  and  value  of  by-products  and  methods  of  obtaining 
same. 

17.  Dumping  ground. 

18.  Inclination  of  surface  of  property. 

These  points  having  been  thoroughly  determined,  and  also 
whether  the  existent  volume  of  material,  together  with  other  condi- 
tions, will  warrant  exploitation  and  the  erection  of  a  plant,  it  should 
be  concluded  from  the  topographic  features  which  methods  of  exploi- 
tation of  the  material  will  be  most  suitable. 

In  determining  the  average  extent  and  depth  of  such  alluvial 
deposits  great  care  must  be  taken  to  ascertain  the  situation  of  the 
old  channels  of  the  streams,  as  many  of  the  deposits  in  bottom  lands 
are  irregular,  so  that  a  true  estimate  of  the  amount  of  gravel  or  sand 
contained  can  be  given  only  after  thorough  testing  by  way  of  sound- 
ings, and  especially  by  opening  test  pits  at  short  distances  from 
each  other.  As  the  percentage  of  the  mineral  contained  in  the 
gravels  is  small  and  the  thickness  of  the  deposit  is  usually  slight,  it 
will  be  realized  that  an  enormous  area  of  gravel  and  sand  deposit 
must  be  within  easy  reach  to  insure  profitable  exploitation.  The 
relation  of  volume  to  richness  is  therefore  a  most  important  con- 
sideration. 

Transportation  is  a  feature  that  has  to  be  well  considered. 

In  sections  in  the  Carolinas  quickly  rising  streams  and  sudden 
torrents  have  destroyed  dams  and  carried  away  sluice  boxes,  imple- 
ments, and  other  materials  obtained  by  hard  labor.  Uncovered 
deposits  have  been  covered  up  again  with  the  sands  and  mud  brought 
from  the  mountains  duiing  such  torrents.  Rich  deposits  have  also 
been  purchased  during  favorable  seasons,  which  could  ordinarily 
be  worked  during  short  periods  only,  on  account  of  lack  of  water  or, 
in  winter,  hard  frozen  gravel,  the  thawing  of  which  was  too  expensive. 
Had  the  conditions  been  properly  studied,  much  loss  might  have  been 
avoided. 


22  MONAZITE,    THORIUM,   AND   MESOTHORIUM. 

Careful  forethought  regarding  a  dumping  ground  should  be  made 
in  all  developments,  for  large  quantities  of  bowlders,  clay,  and  tail- 
ings are  produced.  The  deposits  may  become  choked  because  the 
refuse  material  is  dumped  in  an  undesirable  place,  causing  further  work 
to  be  abandoned,  as  the  removal  of  dump  material  is  costly. 

Clays  give  great  trouble  when  present  as  an  overburden  or,  as  is 
of  frequent  occurrence  in  the  Carolinas,  when  mixed  in  large  quanti- 
ties with  the  gravel.  The  removal  of  the  clayey  overburden  is  much 
more  expensive  than  removal  of  sandy  materials,  and  when  the  clay 
is  mixed  with  gravel  washing  consumes  more  tune  and  large  volumes 
of  water. 

When  clay  is  mixed  with  gravel,  particular  care  must  be  used 
in  removing  it,  as  much  monazite  may  adhere  to  it.  The  clays 
seldom  contain  any  of  the  mineral,  but  the  mineral  becomes  embedded 
in  the  outer  parts  of  the  clay  while  lying  in  the  alluvium.  The 
practice  of  cutting  up  the  clay  is  useless  and  wasteful,  although  this 
method  has  been  followed  by  some  of  the  operators.  It  is  sufficient 
to  wash  the  surface  of  such  clays  carefully  and  then  remove  them 
to  the  dump. 

ATTEMPTS   TO    USE    BY-PRODUCTS. 

Attempts  have  been  made  to  utilize  by-products  from  Carolina 
monazite.  Twenty  tons  or  more  of  ilmenite  has  been  shipped  to 
Europe,  but  could  not  bear  transportation  costs.  Garnets  derived 
from  the  separators  have  been  widely  offered,  but  have  been  found 
to  be  of  no  value  as  abrasives,  the  grains  being  rounded  off  by  the 
constant  friction  while  rolling  along  with  other  sands  in  the  stream 
beds.  The  larger  particles  of  garnets  obtained  by  classification, 
which  could  have  been  crushed,  and  thereby  had  their  sharp  edges 
preserved,  have  been  obtained  in  small  quantities  only  from  the 
monazite  sands. 

In  some  sections  gold  is  found  in  the  concentrates.  Although 
the  amount  so  obtained  has  been  small,  it  has  paid  to  put  aside  the 
residues  after  treatment  by  electromagnetic  methods,  and  then, 
when  sufficient  quantities  have  been  collected,  to  concentrate  them 
on  an  oscillating  table  or  by  some  other  suitable  process.  Although 
the  proportion  of  gold  contained  in  such  sands  is  not  great,  it  has 
been  known  to  have  a  value  of  about  $200  per  30  tons  of  monazite, 
which  is  equal  to  about  1|  cents  per  ton  of  gravel.  This  could  be 
considered  almost  clear  profit,  as  the  extraction  of  the  gold  from  the 
residues  is  inexpensive.  Monazite  sands  purchased  from  gold- 
mining  sections,  which  have  been  treated  for  gold  by  the  miners, 
have,  after  the  separation  of  the  monazite,  yielded  a  further  small 
amount  of  the  precious  metal. 

In  many  sections  "black  sands"  accompany  monazite  in  large 
quantities. 


METHOD   FOR   THE    DETERMINATION    OF   THORIUM    IX    MONAZITE.        23 

In  this  paper  methods  of  treatment  in  actual  use  have  been  de- 
scribed. It  is,  however,  more  than  probable  that  small  dredges 
would  prove  useful  in  the  mining  of  monazite  as  they  have  in  the 
western  field  for  gold. 

METHOD  FOB  THE   DETERMINATION  OF  THORIUM  IN   MONAZITE. 

Many  methods  for  determining  thorium  in  monazite  have  been 
described.  Only  the  following  well-known  method  is  alone  given 
here.0 

About  1  gram  of  the  monazite  is  ground  to  an  impalpable  powder, 
weighed  into  a  platinum  vessel,  covered  with  15  to  20  c.c.  of  con- 
centrated sulphuric  acid,  and  evaporated  until  fumes  are  no  longer 
driven  off.  More  sulphuric  acid  is  added  and  heated  as  before. 
The  operation  is  repeated  several  times  until  the  conversion  of  the 
phosphates  into  sulphates  is  complete.  The  mass  resulting  is  added 
in  small  quantities  to  about  700  c.c.  of  water  at  0°  C.,  with  constant 
stining,  care  being  used  not  to  allow  the  temperature  to  rise  higher 
than  2°  C.  The  solution  is  allowed  to  stand  10  to  12  hours,  when 
it  is  filtered  and  washed.  The  filtrate  is  then  nearly  neutralized 
with  dilute  ammonia,  50  c.c.  of  a  cold  saturated  solution  of  oxalic 
acid  is  added  with  constant  stirring,  and  the  solution  is  allowed 
to  stand  for  12  hours.  The  solution  is  then  filtered  and  the  precipi- 
tate washed  well  with  water.  The  precipitated  oxalates  are  then 
washed  into  a  beaker,  and  treated  with  a  strong  solution  of  caustic 
potash,  heated  to  boiling,  diluted,  and  filtered. 

The  hydroxides  are  washed  thoroughly  with  water  and  dissolved 
off  the  filter  with  hot  dilute  hydrochloric  acid  (1-1).  The  solution 
is  evaporated  to  dryness  to  free  it  from  acid,  taken  up  with  75  to 
100  c.c.  of  water,  15  c.c.  of  a  saturated  solution  of  sodium  thiosul- 
phate  is  added,  and  the  solution  is  heated  to  boiling.  It  is  then 
filtered  and  the  precipitate  and  the  filter  set  aside  for  subsequent 
filtration.  An  excess  of  ammonia  is  added  to  the  filtrate,  the  pre- 
cipitate is  filtered  off,  washed,  dissolved  in  hydrochloric  acid,  and 
evaporated  to  dryness,  the  residue  being  taken  up  in  water  and 
reprecipitated  with  thiosulphate  as  before.  The  solution  is  filtered 
through  the  filter  paper  carrying  the  first  precipitate,  and  the  filtrate 
is  treated  as  before.  The  precipitations  are  continued  as  long  as  the 
precipitate  forms  with  the  thiosulphate,  three  precipitations  usually 
being  sufficient  to  completely  extract  the  thorium.  The  combined 
precipitates  of  thorium-thiosulphate  are  washed  completely,  dried, 
and  ignited.  The  ignited  mass  is  fused  for  some  time  with  potassium 
bisulphate,  taken  up  in  water,  and  a  few  drops  of  hydrochloric  acid 
added,  and  precipitated  with  oxalic  acid.  The  oxalates  are  converted 

a.  SeeMetzger,  F.  J.,  Anew  separation  of  thorium  from  cerium,  lanthanum,  and  didymium,  and  its  appli- 
cation to  the  analysis  of  monazite,  Jour.  Am.  Them.  Soc.,  vol.  24,  1902,  p.  901:  see  also  Levy,  S.  1 .,  The 
rare  earths,  London,  1915,  pp.  2  .5-290. 


24  MONAZITE,    THORIUM,   AND    MESOTHORIUM. 

into  the  hydroxides,  dissolved  in  hydrochloric  acid,  evaporated  to 
dryness,  taken  up  in  water,  and  reprecipitated  with  sodium  thiosul- 
phate,  filtered,  washed,  dried,  ignited,  and  weighed  as  ThO2. 

TREATMENT  OF  MONAZITE  FOB  THE  EXTRACTION  OF  THORIUM. 

Soddy  °  gives  in  a  short  form  the  technical  treatment  of  the 
monazite  sand  as  it  is  carried  on  to-day  in  the  industry. 

In  the  first  stage  of  the  technical  treatment  of  the  monazite  sand, 
which  is  ground  up  very  fine,  it  is  heated  with  twice  its  weight  of 
sulphuric  acid.  The  further  procedure  in  the  treatment  is  described 
by  Soddy  6  as  follows : 

The  cold  mass  is  dissolved  in  water  and  left  to  settle.  The  solution  is  then  frac- 
tionally precipitated  with  magnesia,  the  thorium  being  concentrated  mainly  in  the 
first  fractions  precipitated.  The  commonest  and  most  useful  reagent  for  precipitating 
the  rare  earths  from  a  solution  containing  common  earths  such  as  alumina,  iron,  etc., 
is  oxalic  acid.  Now  thorium  oxalate  is  of  all  the  rare-earth  oxalates  the  least  soluble 
in  acids,  so  that  by  working  in  fairly  strong  nitric  acid  solution  thorium  oxalate  may 
often  be  precipitated  and  separated  at  least  partially  from  the  other  rare  earths  and 
from  calcium.  The  same  is  true  of  the  rare-earth  phosphates,  that  of  thorium  being 
one  of  the  most  insoluble  in  dilute  acids.  On  the  same  principle  thorium  is  often 
precipitated  by  weak  bases,  such  as  the  substituted  ammonias,  for  example,  dimethyla- 
mine,  while  zirconium,  etc.,  remain  dissolved.  The  potassium  salt  of  hydrazoic 
acid,  KN3,  precipitates  thorium  hydroxide  only  from  mixtures  of  thorium  and  cerium 
on  boiling.  The  same  separation  may  be  effected  by  means  of  sodium  thiosulphate 
on  boiling,  thorium  alone  being  separated,  as  hydroxide.  This  ready  hydrolysis  of 
weak  thorium  is  characteristic  of  the  element.  The  oxalatos  of  thorium  and  zirconium 
alone  of  the  rare  earths  are  soluble  in  ammonium  oxalate,  and  on  strongly  acidifying 
the  solution  the  former  alone  is  reprecipitated.  The  solution  of  the  oxalate  of  tho- 
rium and  its  conversion  into  soluble  salts  may  be  effected  by  means  of  concentrated 
ammonium  or  sodium  carbonate  and  precipitation  of  the  concentrated  solution  as 
thorium  hydroxide  with  strong  ammonium  or  sodium  hydrate.  Thorium  is  distin- 
guished from  the  yttrium  group  of  the  rare  earths  by  ite  power  of  forming  a  double 
sulphate  with  potassium  sulphate,  insoluble  in  excess  of  the  latter  reagent,  and  so 
may  be  separated  from  a  mixture  of  the  sulphates  by  saturating  the  solution  with 
potassium  sulphate.  Alike  in  the  old,  now  obsolete,  as  in  the  present,  technical 
methods  of  purifying  thorium,  the  peculiar  solubility  relations  of  thorium  sulphate 
in  water  have  been  largely  applied.  The  older  method  consisted  in  volatilizing  the 
excess  of  sulphuric  acid  from  the  material  being  treated,  and  in  dissolving  the 
anhydrous  sulphates  in  ice-cold  water — a  tedious  operation — and  in  heating  the 
solution  till  the  hydrated  thorium  sulphate  was  precipitated.  The  latter  was  then 
dehydrated, at  300°  to  400°  and  the  process  repeated.  In  present  practice  the  sul- 
phuric acid  is  always  kept  in  great  excess  in  the  initial  treatment  of  the  mineral, 
but  the  sulphate  method  may  be  employed  at  the  final  stage  of  manufacture  as  follows: 

The  thorium  hydroxide  is  dissolved  in  hydrochloric  acid,  so  that  the  solution 
contains  not  more  than  30  per  cent  ThO2,  and  sulphuric  acid  is  added  to  the  extent 
of  0.5  per  cent  more  than  the  equivalent  quantity,  the  temperature  being  kept  low, 
and  in  any  case  below  40°  as  a  maximum.  ,  Under  these  conditions  the  hydrate 
Th(SO4)28H2O  is  precipitated,  departure  from  the  conditions  causing  the  separation 

a  Soddy,  Frederick,  The  chemistry  of  the  radio  elements,  1911,  pp.  64-69;  see  also,  Bohm.,  Richard,  Die 
Darstellung  der  seltenen  Erden,  Leipzig,  1905,  vol.  2,  pp.  94-98;  Levy,  S.  I.,  The  rare  earths,  Lon- 
don, 1915,  pp.  276-285. 

b  Soddy,  Frederick,  loc  cit. 


SEPARATION    OF    MESOTHORIUM    OX    A    COMMERCIAL    SCALE.       25 

of  the  tetrahydrate,  which  is  in  every  way  less  easily  manipulated.  The  precipitated 
sulphate  is  reconverted  into  hydroxide,  and  the  process  repeated  as  often  as  necessary 
to  remove  all  impurities. 

Thorium  forms  a  curious  compound  with  acetyl  acetone,  Th(C5H7O2)4,  which  is 
soluble  in  chloroform  and  alcohol,  and  can  be  distilled  in  a  vacuum,  and  so  can 
advantageously  be  employed  for  the  purification  and  separation  of  the  element. 

It  may  be  mentioned  that  in  the  fusion  of  refractory  minerals,  as  with  sodium 
carbonate,  the  thorium,  if  present,  is  converted  into  the  highly  insoluble  oxide, 
Th02,  and  its  presence  is  apt  to  be  overlooked  . 

Thanks  largely  to  the  thorium  industry,  in  which  a  product  unusually  pure  Is 
essential,  there  exist,  therefore,  a  great  variety  of  exceedingly  good  and  sharp  methods 
for  the  separation  and  purification  of  thorium,  and  it  muet  be  understood  that  ionium, 
if  present,  and  radio-thorium  always  remain  unseparated  from  thorium  in  these 
processes  as  far  as  they  have  been  examined. 

In  the  manufacture  of-  thorium  nitrate  from  monazite  a  large  amount 
of  residues  of  the  cerium  group  of  rare  earths  is  ob  tamed.  Monazite  con- 
tains 60  to  70  per  cent  of  the  cerium  group  or  other  rare  earths  besides 
thorium,  and  3,000  tons,  which  is  the  annual  consumption  of  mona- 
zite, gives  about  1,000  tons  of  cerium  and  about  1,200  tons  of  a  mix- 
ture of  the  rare  earths,  lanthanum,  neodymium,  and  praesodymium 
oxides.  Considerable  research  work  has  been  done  in  order  to  utilize 
these  waste  materials,  and  experiments  have  been  made  with  almost 
every  one  of  them.  In  order  to  obtain  and  separate  the  rare-earth 
elements,  thousands  of  crystallizations  and  fractionations  are  neces- 
sary, although  cerium  itself  is  separated  with  comparative  ease.  The 
untiring  work  carried  on  in  the  research  laboratories  of  the  industries 
as  well  as  by  the  scientists  in  both  America  and  in  Europe  will,  no 
doubt,  in  time  be  crowned  with  successful  technical  applications  of 
the  by-products. 

SEPARATION  OF  MESOTHORIUM  ON  A  COMMERCIAL  SCALE. 

Monazite  sand  is  the  main  source  of  mesothorium  and  contains  also 
uranium  and,  consequently,  radium.  Mesothorium  has  properties 
similar  to  radium,  and  the  radium  therefore  is  separated  together  with 
the  mesothorium.  The  methods  employed  in  the  extraction  of  meso- 
thorium are  well  known  and  have  been  described  by  Haitinger  and 
Ulrich  °,  and  have  been  used  in  the  extraction  of  radium.6 

Some  manufacturers  of  mesothorium  add  a  small  quantity  of  barium 
sulphate  to  the  monazite  sand  during  its  treatment  with  sulphuric 
acid,  whereby  the  mesothorium  is  separated  with  the  insoluble  material 
left  after  the  treatment  of  the  product  with  water. 

The  half-value  period  or  period  of  half  life  (the  time  required  in 
which  one-half  of  any  given  quantity  of  radioactive  matter  disinte- 
grates —  becomes  transformed  —  is  called  half-value  period  or  period  of 


o  Haitinger,  Ludwig,  and  Ulrich,  Karl,  Bericht  iiber  die  BearbeitiniK  der  Pechblendo 
Her.  K.  Akad.  Wiss.,  vol.  117,  1908,  p.  619. 

6  Moore,  R.  B.,  and  Kithil,  K.  L.,  A  preliminary  report  on  uranium,  radium,  and  vanadium:  Bull.  70, 
Bureau  of  Mines,  1914,  p.  79. 


26  MONAZITE,   THORIUM,  AND   MESOTHORIUM. 

half  life)  of  meso thorium  is  5.5  years,  whereas  that  of  radium  is  ahout 
2,000  years. 

The  manufacture  of  mesothorium  alone  from  monazite  is  not  prof- 
itable, as  the  value  of  the  mesothorium  extracted  would  not  pay  for 
the  cost  of  the  monazite.  As  a  by-product  from  thorium  nitrate  man- 
ufacture such  manufacture  should  be  of  importance. 

QUANTITATIVE  DETERMINATION  OF  MESOTHORIUM. 

The  quantitative  determination  of  mesothorium  is  carried  on  in 
the  same  manner  as  for  radium.0 

The  content  of  mesothorium  in  preparations,  all  of  which  carry 
about  25  per  cent  of  radium,  is  expressed  in  terms  of  the  gamma  ray 
activity  of  radium  in  equilibrium.  For  example,  5  milligrams  of 
mesothorium  on  this  standard  indicates  that  the  gamma  ray  activity 
of  the  mesothorium  plus  the  radium  contained  in  it  one  month  after 
separation  gives  a  gamma  ray  activity  equal  to  that  of  5  milligrams 
of  pure  radium  bromide. 

If  both  the  radium  and  the  mesothorium  are  to  be  determined  then 
radium  plus  mesothorium  is  determined  by  means  of  the  gamma  ray 
method,  and  afterwards,  by  the  emanation  method,  the  radium  alone 
is  determined. 

By  the  gamma  ray  method  alone  can  be  determined  the  ratio  of 
radium  to  mesothorium  by  measuring  the  gamma  rays  before  and 
after  boiling  the  solutions.  The  content  of  mesothorium  plus  radium 
is  found  before  the  solution  is  boiled ;  after  it  has  been  boiled,  the  con- 
tent of  mesothorium  alone  is  given,  as  the  radium  emanation  is  re- 
moved by  boiling,  and  radium  Ct,  which  emits  the  gamma  rays,  is,  for 
all  practical  purposes,  disintegrated  after  three  hours'  time. 

In  regard  to  the  method  of  measuring  mesothorium  and  radium  by 
the  gamma  ray  method,  reference  is  made  to  the  work  of  Ebler,b  and  of 
Meyer  and  Hess.c 

The  quantities  of  mesothorium  that  can  be  extracted  from  monazite 
are,  of  course,  very  small.  One  hundred  metric  tons  of  monazite  with 
a  content  of  5  per  cent  ThO2  contains  approximately  4.3  tons  of  tho- 
rium metal.  According  to  Rutherford, d  one  metric  ton  of  thorium 
metal  contains  0.42  milligram  of  mesothorium.  We  have,  therefore, 
0.42  milligram  of  mesothorium  per  weight  of  10~6  grams  of  tho- 
rium, or  4.3  times  0.42,  equals  1.8  milligrams  of  mesothorium  by 
weight.  The  activity  due  to  mesothorium  is  three  times  as  great  as 

o  Soddy,  Frederick,  The  chemistry  of  the  radio  elements,  1911,  pp.  46-49;  Rutherford,  E.,  Radioactive 
substances  and  their  radiations,  1913,  p.  550. 

6  Ebler,  Erich,  Chemiker  Kalender  for  1914,  vol.  2,  pp.  371-372. 

c  Meyer,  Stefan,  and  Hess,  V.  F.,  Gamma  Strahlenmessung  von  Meso-thorpriiparaten:  Mitt.  Inst.  Ra- 
diumforschung,  Vienna,  July  2, 1914,  pp.  1443-1458. 

d  Rutherford,  E.,  Radioactive  substances  and  their  radiations,  1913,  p.  552. 


MONAZITE    SANDS. 


27 


that  due  to  radium  when  compared  weight  with  weight.  The  meso- 
thorium  obtained  from  one  ton  of  monazite,  therefore,  would  be  cal- 
culated as  5.4  milligrams.  Lorenzen,0  however,  states  that  tech- 
nically 2.5  milligrams  of  mesothorium  can  be  obtained  from  1  metric 
ton  of  monazite,  or  100  tons  of  monazite  would  yield  250  milligrams 
of  mesothorium.  It  seems,  therefore,  that  technically  a  recovery  of 
about  50  per  cent  is  made.  Mesothorium  is  sold  on  the  basis  of  its 
activity  compared  with  radium  bromide  of  highest  purity  (determined 
by  the  gamma  ray  method),  and  has  been  sold  with  increasing  de- 
mand at  $45  to  $60  per  milligram.  The  separation  of  mesothorium 
has  been  widely  discussed  in  scientific  and  technical  papers  and  is 
outlined  on  page  25. 

The  manufacture  of  thorium  nitrate  from  monazite  is  well  known 
and  has  been  described  extensively.  This  manufacture,  however,  is 
briefly  described  on  pages  24-25.  The  manufacture  of  the  thorium 
nitrate  is  so  highly  developed  that  a  recovery  of  90  to  95  per  cent  of 
the  thorium  contained  in  the  monazite  has  been  made  by  many  indus- 
trial concerns. 

Although  in  former  years  monazite  and  thorium  nitrate  were 
imported  into  this  country,  lately,  since  the  manufacture  of  meso- 
thorium from  the  thorium  residues  has  been  begun,  Europe  prefers 
to  export  the  ash  of  the  broken  incandescent  mantles,  which  are  high 
in  ThO2,  and  keeps  the  monazite  in  order  to  obtain  the  mesothorium 
from  the  residues.  The  import  duty  on  the  ash  brought  into  the 
United  States  is  only  10  per  cent  ad  valorem,  whereas  thorium  nitrate 
pays  25  per  cent  duty.  The  thoria  ash  has  been  sold  for  25  marks 
($6)  per  kilogram  in  Europe. 

MINERALS  IN  MONAZITE  SANDS. 

The  minerals  contained  in  monazite  sands,  arranged  according  to 
their  specific  gravity,  are  shown  in  the  tabulation  following: 

Minerals  contained  in  monazite  sands,  arranged  according  to  specific  gravity. 


Letter 

Letter 

showing 

showing 

Mineral. 

Specific 
gravity. 

relative 
quantita- 
tive oc- 

Mineral. 

Specific 
gravity. 

relative 
nuantita- 
tive  oc- 

currence.!) 

currence^ 

2  05 

Rutile 

42   to  4  25 

| 

Feldspar 

2.5    to  2.7 

Zircon  

4.5    to  4.  7 

i 

Tourmaline  

3.0   to  3.  2 

Ilmenite  

4.5    to5 

6 

Apatite  

Epidote 

3.2   to  3.  25 
3.2   to  3.  5 

9 

Monazite  
Magnetite  

4.8   to5.3 
5.  16  to  5.  18 

t 

Ouvine 

33    to  3.  6 

Gold  

15       to  19 

k 

Garnet  

3.8   to  4.  3 

c 

a-  Private  information  received  from  Juliu.s  Lorenzen,  Tegel-Berlin,  on  Chemical  Manufacture  of  Meso- 
thorium. 
6  The  order  varies  according  to  localities. 


28 


MONAZITE,   THORIUM,   AND   MESOTHOEIUM. 


The  conglomerate  must  be  freed  from  the  larger  gravels  and  from 
the  clays. 

Proper  sizing  is  important  before  concentration;  in  sizing  the 
remaining  clay  and  mica  particles  should  be  removed  by  a  sliming 
process. 

Four  or  five  sizes  should  be  made  through  sieves  of  20,  50,  80,  and 
100  mesh. 

Such  properly  sized  material  when  treated  on  the  large  type  of 
Wetherill  electromagnetic  separator,  having  two  magnets  and  18-inch 
belt,  gives  the  following  results : 
Results  of  action  of  Wetherill  electromagnetic  separator  on  properly  sized  monazite  sands. 


Mineral." 

| 

Point  in  separator  at  which  mineral  separated. 

Current. 

Magnetite                                 ' 

Ilmenite  1 

Hematite  i 

Platinum  (if  any)  

Epidote  
Apatite 

Second  pole,  first  magnet;  distance  between  poles,  about 

peres. 

Olivine  ."  
Tourmaline  

Monazite  (92  to  95  per  cent) 
and  traces  of  zircon  and 
rutile. 
Platinum,  etc.  (if  any)  

First  and  second  pole  of  second  magnet;  distance,  first  pole, 
6  mm.;  second  pole,  2  to  3  mm. 

12  to  15  am- 
peres. 

1 

«  Residues  off  belt  were  quartz,  feldspar,  gold,  zircon,  rutile,  etc. 

Data  showing  fluctuation  of  prices  for  thorium  nitrate  for  use  in  incandescent  gas 
mantles.0 


Europe 
(per  kilo). 

United 
States  (per 
pound).* 

1894                                                                                                         .       .   

Marks. 
2,000 
900 
500 
300 
150 
96 
60 
40 
30 
28 
36 
43 
43 
43 
43 
27 
32 
32 
32 
27 
19 
17 
22 
22 
21 
21 
22 
22 

Dollars. 

1895  July 

1895,  November        .                                       .  .             

1896,  early  part  
1896  later  part 

1897 

1898 

1899 

1900 

1902                                                            

5.86 
5.86 
6.10 
6.53 
3.78 
3.93 
4.65 
4.70 
3.87 
3.20 
3.00 
3.00 
3.00 
2.85 
2.60 
2.71 
3.25 

1904,  later  part  

1006 

1907,  early  part.... 

1907  later  part 

1908*             .  .                      

1909 

1910  later  part 

Will  
1912 

1913,  later  part  

1914,  early  part  
1914,  later  part 

Price  of  thorium 
nitrate. 


"Import  duty  on  thorium  nitrate  brought  into  the  United  States,  25  per  cent  ad  valorem. 
6I)ata  furnished  by  Dr.  Hugo  Liebcr,  25  Madison  Avenue,  New  York,  N.  Y. 


MINERALS  IX    MONAZITE    SANDS. 
FLOW    SHEET. 

A  flow  sheet  of  the  separation  process  is  shown  in  figure  1. 


29 


I 


Zircon  and  rutile 


Quartz  and  f  eld- 
spar 


Slime  and  lighter 
materials 


FIGURE  1. — Flow  sheet,  showing  steps  in  process  of  magnetic  separation  of  monazite  sands. 


SELECTED  BIBLIOGRAPHY. 

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-  Die  Venvendung  der  seltenen  Erden,  Leipzig,  1913. 

-  Monazite  sand:  Eng.  and  Min.  Jour.,  vol.  81,  May  5,  1906,  p.  842. 

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DAY,  D.  T.,  and  RICHARDS,  R.  H.  Useful  minerals  in  the  black  sands  of  the  Pacific 
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GUNTHER,  G.  G.     Electromagnetic  ore  separation,  1909,  193  pp. 

JOURNAL  OF  THE  FRANKLIN  INSTITUTE.  Report  on  Welsbach  light,  by  Committee  on 
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JOHNSTONE,  S.  J.  Monazite  from  some  new  localities:  Jour.  Soc.  Chem.  Ind.,  vol. 
33,  January  31,  1914,  pp.  55-59. 

LANEY,  F.  B.,  and  WOOD,  K.  H.  Bibliography  of  North  Carolina  geology,  miner- 
alogy, and  geography:  N.  C.  Geol.  and  Econ.  Survey  Bull.  IS,  1909.  Gives  a 
comprehensive  bibliography  concerning  monazite  deposits  in  North  Carolina. 

LEVY,  S.  I.  The  rare  earths,  their  occurrence,  chemistry,  and  technology.  London, 
1915,  345  pp. 

LINDGREN,  WAI.DEMAR.  Mining  district  of  Idaho  Basin  and  Boise  Ridge:  U.  ,S.  Geol. 
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METZGER,  F.  J.,  and  ZONS,  F.  W.  A  volumetric  method  for  the  determination  of 
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MINING  REPORTER.  The  industrial  position  of  thorium.  Vol.  53,  February  22,  1906, 
p.  190. 

NITZE,  H.  B.  C.  Monazite,  U.  S.  Geol.  Survey,  Sixteenth  Annual  Report,  pt.  4, 1896, 
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PRATT,  J.  H.    Monazite:  U.  S.  Geol.  Survey,  Mineral  Resources,  1901-1905. 
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of  magnetic  ore  concentration. 
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Bull.  430,  1910,  pp.  184-191. 
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-  Monazite  deposits  of  the  Carolinas:  U.  S.  Geol.  Survey  Bull.  340,  1908,  pp. 
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30 


PUBLICATIONS  ON  MINERAL  TECHNOLOGY. 

A  limited  supply  of  the  following  publications  of  the  Bureau  of 
Mines  is  temporarily  available  for  free  distribution.  Requests  for 
all  publications  can  not  be  granted,  and  to  insure  equitable  distribu- 
tion applicants  are  requested  to  limit  their  selection  to  publications 
that  may  be  of  especial  interest  to  them.  Requests  for  publications 
should  be  addressed  to  the  Director,  Bureau  of  Mines. 

'BULLETIN  3.  The  coke  industry  of  the  United  States  as  related  to  the  foundry,  by 

Richard  ^1enke-     191°-     32PP- 

BULLETIN,  " n  Apparatus  and  methods  for  the  sampling  and  analysis  of  furnace  gases, 
by  J  C.  W.  j  :azer  and  E.  J.  Hoffman.  1911.  22  pp.,  6  figs. 

BULLETI!    •*>•  The  uses  of  peat  for  fuel  and  other  purposes,  by  C.  A.  Davis.     1911. 

214pp..  I*'1-'  !"*«• 

-gT^LETiN  42.  The  sampling  and  examination  of  mine  gases  and  natural  gas,  by  G. 
Burrell  and  F.  M.  Seibert.     1913.     116  pp.,  2  pis.,  23  figs. 

BULLETIN  45.  Sand  available  for  filling  mine  workings  in  the  northern  anthracite 
coal  basin  of  Pennsylvania,  by  N.  H.  Darton.  1913.  33  pp.,  8  pis.,  5  figs. 

BULLETIN  47.  Notes  on  mineral  wastes,  by  C.  L.  Parsons.     1912.    44  pp. 

BULLETIN  53.  Mining  and  treatment  of  feldspar  and  koalin  in  the  southern  Appa- 
lachian region,  by  A.  S.  Watts.  1913.  170  pp.,  16  pis.,  12  figs. 

BULLETIN  64.  The  titaniferous  iron  ores  of  the  United  States,  their  composition  and 
economic  value,  by  J.  T.  Singewald,  jr..  1913.  145  pp.,  16  pis.,  3  figs. 

BULLETIN  70.  A  preliminary  report  on  uranium,  radium,  and  vanadium,  by  R.  B. 
Moore  and  K.  L.  Kithil.  1913.  101  pp.,  4  pis.,  2  figs. 

BULLETIN  71.  Fuller's  earth,  by  C.  L.  Parsons.     1913.    38  pp. 

BULLETIN  81.  The  smelting  of  copper  ores  in  the  electric  furnace,  by  D.  A.  Lyon 
and  R.  M.  Keeney.  1914.  80  pp.,  6  figs. 

BULLETIN  84.  Metallurgical  smoke,  by  C.  H.  Fulton.     1914.     94  pp.,  6  pis.,  15  figs. 

BULLETIN  85.  Analyses  of  mine  and  car  samples  of  coal  collected  in  the  fiscal  years 
1911  to  1913,  by  A.  C.  Fieldner,  H.  I.  Smith,  A.  H.  Fay,  and  Samuel  Sanford.  1914. 
444pp.,  2  figs. 

TECHNICAL  PAPER  3.  Specifications  for  the  purchase  of  fuel  oil  for  the  Government. 
with  directions  for  sampling  oil  and  natural  gas,  by  I.  C.  Allen.  1911.  13  pp. 

TECHNICAL  PAPER  8.  Methods  of  analyzing  coal  and  coke,  by  F.  M.  Stanton  and 
A.  C.  Fieldner.  1913.  42  pp.,  12  figs. 

TECHNICAL  PAPER  14.  Apparatus  for  gas-analysis  laboratories  at  coal  mines,  by 
G.  A.  Burrell and  F.M.  Seibert.  1913.  24  pp.,  7 figs. 

TECHNICAL  PAPER  38.  Wastes  in  the  production  and  utilization  of  natural  gas,  and 
means  for  their  prevention,  by  Ralph  Arnold  and  F.  G.  Clapp.  1913.  29  pp. 

TECHNICAL  PAPER  39.  The  inflammable  gases  in  mine  air,"  by  G.  A.  Burrell  and 
F.  M.  Seibert.  24  pp.,  2  figs. 

TECHNICAL  PAPER  41.  Mining  and  treatment  of  lead  and  zinc  ores  in  the  Joplin 
district,  Missouri;  a  preliminary  report,  by  C.  A.  Wright.  1913.  43  pp.,  5  figs. 

TECHNICAL  PAPER  43.  The  influence  of  inert  gases  on  inflammable  gaseous  mixtures, 
by  J.  K.  Clement.  1913.  24  pp.,  1  pi.,  8  figs. 

TECHNICAL  PAPER  50.  Metallurgical  coke,  by  A,  W.  Belden.  1913.  48  pp.,  1  pi., 
23  figs. 

31 


32  MONAZITE,    THORIUM,   AND    MESOTHORIUM. 

TECHNICAL  PAPER  60.  The  approximate  melting  points  of  some  commercial  copper 
alloys,  by  H.  W.  Gillett  and  A.  B.  Norton.  1913.  10  pp.,  1  fig. 

TECHNICAL  PAPER  66.  Mud-laden  fluid  applied  to  well  drilling,  by  J.  A.  Pollard  and 
A.  G.  Heggem.  1914.  21  pp.,  12  figs. 

TECHNICAL  PAPER  70.  Methods  of  oil  recovery  in  California,  by  Ralph  Arnold  and 
V.  R.  Garfias.  1914.  57  pp.,  7  figs. 

TECHNICAL  PAPER  76.  Notes  on  the  sampling  and  analysis  of  coal,  by  A.  C.  Fieldner. 

1914.  59  pp.,  6  figs. 

TECHNICAL  PAPER  81.  The  vapor  pressure  of  arsenic  trioxide,  by  L.  H.  Duschak. 

1915.  22  pp.,  2  figs. 

TECHNICAL  PAPER  88.  The  radium-uranium  ratio  in  carnotites.  by  S.  0.  Lind  :uid 
.C.  F.  Whittemore.  1915.  29  pp.,  1  pi.,  4  figs. 

TECHNICAL  PAPER  89.  Coal-tar  products,  and  the  possibility  of  their  successful 
manufacture  in  the  United  States,  by  H.  C.  Porter,  with  a  chapter  on  coal-tar  prod- 
ucts used  in  explosives,  by  C.  G.  Storm.  1915.  21  pp. 

TECHNICAL  PAPER  90.  Metallurgical  treatment  of  the  low-grade  am)  (.n,,.j,iex  on,s 
of  Utah;  a  preliminary  report,  by  D.  A.  Lyon,  R.  H.  Bradford,  S.  S-  J^entz  Q  <• 
Ralston,  and  C.  L.  Larson.  1915.  40  pp. 

TECHNICAL  PAPER  95.  Mining  and  milling  of  lead  and  zinc  ores  in  tru 
district,  Wisconsin,  by  C.  A.  Wright.     1915.     39  pp.,  2  pis.,  5  figs. 

TECHNICAL  PAPER  99.  Probable  effect  of  the  war  in  Europe  on  the  ceramic'  iml., 
tries  of  the  United  States,  by  A.  S.  Watte.     1915.     15  pp. 

o 


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